Beschreibung: Microplastic particles are ubiquitous in the environment, from the air we breathe to the food we eat. The key question with respect to these particles is to what extent they cause risks for the environment and human health. There is no risk assessment framework that takes into account the multidimensionality of microplastic particles against the background of numerous natural particles, which together encompass an infinite combination of sizes, shapes, densities and chemical signatures. We review the current tenets in defining microplastic characteristics and effects, emphasizing advances in the analysis of the diversity of microplastic particles. We summarize the unique characteristics of microplastic compared with those of other environmental particles, the main mechanisms of microplastic particle effects and the relevant dose metrics for these effects. To characterize risks consistently, we propose how exposure and effect thresholds can be aligned and quantified using probability density functions describing microplastic particle diversity.

Beschreibung: Microplastics (MP) are of major concerns for the society and currently in the focus of legislators and administrations. A small number of measures to reduce or remove primary sources of MP to the environment are currently coming into effect. At the moment, they have not yet tackled important topics such as food safety. However, recent developments such as the 2018 bill in California are requesting the analysis of MP in drinking water by standardized operational protocols (SOP). Administrations and analytical labs are facing an emerging field of methods for sampling, extraction and analysis of MP, which complicate the establishment of SOPs. In this review the state of the currently applied identification and quantification tools for MP are evaluated providing a harmonized guideline for future SOPs to cover these types of bills. The main focus is on the naked eye detection, general optical microscopy, the application of dye staining, flow cytometry, Fourier-Transform Infrared (FTIR) spectroscopy and microscopy, Raman spectroscopy and microscopy and thermal degradation by pyrolysis gas-chromatography/mass spectrometry (Py-GC/MS) as well as thermo-extraction and desorption gas-chromatography/mass spectrometry (TED-GC/MS). Additional techniques are highlighted as well as the combined application of the analytical techniques suggested. An outlook is given on the emerging aspect of nanoplastic analysis. In all cases, the methods were screened for limitations, field work abilities and, if possible, estimated costs and summarized into a recommendation for a work-flow covering the demands of society, legislation and administration in cost efficient but still detailed manner.

Beschreibung: The environmental pollution with small plastic particles was recognized in the early 70s (Carpenter & Smith 1972). Today these plastics can be found in every marine habitat and are expected to have enormous negative impacts. The smaller the items get through fragmentation the more organisms can feed on them. Zooplankters cannot discriminate while feeding and can absorb POPs or other chemicals adhered to ingested plastics which then have the potential to accumulate in the marine food chain (Cole et al 2013). The term microplastic includes all plastics smaller than 5 mm: These can be released directly as primary microplastic in cosmetics and in form of lost industrial pellets or through fragmentation of larger plastic items (secondary microplastics). Introduced in the environment, plastics cannot be mineralized, but UV- radiation and physical wave actions will lead to the embrittlement and further fragmentation of plastics. Because of this even a direct stop of plastic introduction would lead to an increasing amount of microplastics in the marine environment (Cole et al 2011). Until now nonexistent methods made the detection of microscopic plastics that are smaller than 500 µm impossible and so most of the published studies focus on the visual sorting and determination of samples taken in marine sediments or at the water surface. The new combination of micro- Fourier transform infrared spectroscopy (FTIR) with a focal plane array detector (FPA) is highly promisingly for this (Harrison et al 2012). But to enable this way of analysis a sufficient sample purification is needed that removes all disturbing natural materials without affecting the plastic particles. A method was developed that combines enzymatic digestion with density separation using a ZnCl2 solution. This method allows for the first time the examination of all microscopic plastics of complete plankton samples taken from coastal waters of the German North and Baltic Sea. Although plastic introduction from the high shipping activities and additional landbased sources can be expected in the region, there is little knowledge about large- scale planktonic microplastic concentrations. 28 stations were sampled and the total concentrations of visible and microscopic plastics determined which ranged considerably from 0 to 3.5 items m-3. An outstanding high concentration of 1.3 visible plastics m-3 and the detection of same PE pellets in 2012 and 2013 at the western coast of Denmark could suggest an accumulation zone in this area. A fact that may be supported by the findings of Galgani et al (2000) who found considerably higher plastic concentrations in an 190 large area 200 km away from the Danish coast when examining sedimented macroplastics.

Beschreibung: The global presence of microplastic (MP) in aquatic ecosystems has been shown by various studies. However, neither MP concentrations nor their sources or sinks are completely known. Waste water treatment plants (WWTPs) are considered as significant point sources discharging MP to the environment. This study investigated MP in the effluents of 12 WWTPs in Lower Saxony, Germany. Samples were purified by a plastic-preserving enzymatic-oxidative procedure and subsequent density separation using a zinc chloride solution. For analysis, attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FT-IR) and focal plane array (FPA)-based transmission micro-FT-IR imaging were applied. This allowed the identification of polymers of all MP down to a size of 20 μm. In all effluents MP was found with quantities ranging from 0 to 5 × 101 m-3 MP 〉 500 μm and 1 × 101 to 9 × 103 m-3 MP 〈 500 μm. By far, polyethylene was the most frequent polymer type in both size classes. Quantities of synthetic fibres ranged from 9 × 101 to 1 × 103 m-3 and were predominantly made of polyester. Considering the annual effluxes of tested WWTPs, total discharges of 9 × 107 to 4 × 109 MP particles and fibres per WWTP could be expected. Interestingly, one tertiary WWTP had an additionally installed post-filtration that reduced the total MP discharge by 97%. Furthermore, the sewage sludge of six WWTPs was examined and the existence of MP, predominantly polyethylene, revealed. Our findings suggest that WWTPs could be a sink but also a source of MP and thus can be considered to play an important role for environmental MP pollution.

Beschreibung: Understanding the multidimensionality of microplastics is essential for a realistic assessment of the risks these particles pose to the environment and human health. Here, we capture size, shape, area, polymer, volume and mass characteristics of 〉60,000 individual microplastic particles as continuous distributions. Particles originate from samples taken from different aquatic compartments, including surface water and sediments from the marine and freshwater environment, waste water effluents, and freshwater organisms. Data were obtained using state-of-the-art FTIR-imaging, using the same automated imaging post-processing software. We introduce a workflow with two quality criteria that assure minimum data quality loss due to volumetric and filter area subsampling. We find that probability density functions (PDFs) for particle length follow power law distributions, with median slopes ranging from 2.2 for marine surface water to 3.1 for biota samples, and that these slopes were compartment-specific. Polymer-specific PDFs for particle length demonstrated significant differences in slopes among polymers, hinting at polymer specific sources, removal or fragmentation processes. Furthermore, we provide PDFs for particle width, width to length ratio, area, specific surface area, volume and mass distributions and propose how these can represent the full diversity of toxicologically relevant dose metrics required for the assessment of microplastic risks.